How do Force Fields Occupy Space?

[PairTheBoard]

An electron has a Force Field around it which acts to repel other electrons and attract positively charged protons.

A moving electron generates a Magnetic Force Field which acts to attract or repel other magnetic objects.

There are also force fields created by strong and weak nuclear forces.

There is also the Gravitational Force Field which extends through space by actually deforming the space-time continuum. But how do the electic, magnetic, strong, and weak force fields extend through space and occupy it? They don't bend space like gravity. They aren't physical objects in the sense of having mass of their own. Yet somehow they reach out through space to attract or repel other objects with similiar force fields of their own. What are these things called force fields exactly?

PairTheBoard

[Zygote]

[ QUOTE ]
What are these things called force fields exactly?

[/ QUOTE ]

x-men

[Phil153]

There's no such thing as a force field , it's just a name we use to make the concept intuitive.

All we know is that when two objects are placed near each other, they start moving toward each other. The rest is still a mystery I believe, but I've been out of the loop a long time.

[madnak]

This is what I want to understand most about physics, but I don't understand it. I've heard it has something to do with photon emission (from electrons) - photons "carry" the "message" to the protons.

I don't think anyone knows about gravity, but I think the "graviton" has been postulated to "carry" the field.

[Metric]

A quote from Rovelli's "Quantum Gravity":

"In newtonian and special-relativistic physics, if we take away the dynamical entities -- particles and fields -- what remains is space and time. In general-relativistic physics, if we take way the dynamical entities, nothing remains. The space and time of Newton and Minkowski are re-interpreted as a configuration of one of the fields, the gravitational field. This implies that physical entities -- particles and fields -- are not immersed in space, and moving in time. The do not live on spacetime. They live, so to say, on one another.

It is as if we had observed in the ocean many animals living on an island: animals on the island. Then we discover that the island itself is in fact a great whale. So the animals are no longer on the island, just animals on animals. Similarly, the Universe is not made up of fields on spacetime; it is made up of fields on fields."

[Kaj]

[ QUOTE ]
This is what I want to understand most about physics, but I don't understand it. I've heard it has something to do with photon emission (from electrons) - photons "carry" the "message" to the protons.

I don't think anyone knows about gravity, but I think the "graviton" has been postulated to "carry" the field.

[/ QUOTE ]

The problem with thinking like this is it assumes that particles (and thus all physical entities) are distinct "things" that need some media to communicate their presence with each other. I believe that more and more we are learning that this view is flawed and that "things" don't exist distinctly. I think each particle (and thus each physical entity) is a "field" in itself and can't be separated out completely to a point in space-time that we observe. We're all fields, man. Hey stop tickling me.

[borisp]

Since you are a math guy, start here:

wiki (http://en.wikipedia.org/wiki/Connection_%28mathematics%29)

Basically, the presence of particles, or virtually anything, changes the metric of whatever manifold you are looking at. (Or it changes the Hamiltonian, whatever.) The effect is that the Levi-Civita connection (or whatever structure you are considering on your manifold) is changed, which means that geodesics (or your Lagrangian submanifold) get changed. This is the fundamental paradigm of general relativity.

So when a charged particle is present, the geodesics of nearby charged particles get changed.

Finally, in physics lingo, particles choose paths that are critical points for the "action." In other words, they try to minimize the "work" that they have to do, or at least try to find a path that is a local minimum (the mathematics is essentially the same as 1st semester calculus where one finds local minima via the derivative, etc. Look up the calculus of variations.)

Anyway, this is not really my area of expertise, so there may be technical difficulties in my exposition. But the general idea is that "fields" are simply attributes of the manifold (usually some sort of configuration space) that one must take into consideration in any physical problem. Strictly speaking, they are smooth functions from M to E, where M is your manifold, and E is some sort of bundle over your manifold.

[thylacine]

[ QUOTE ]
There's no such thing as a force field , it's just a name we use to make the concept intuitive.

All we know is that when two objects are placed near each other, they start moving toward each other. The rest is still a mystery I believe, but I've been out of the loop a long time.

[/ QUOTE ]

Oh that's so 18th Century. You really have been out of the loop.

[PairTheBoard]

[ QUOTE ]
But the general idea is that "fields" are simply attributes of the manifold (usually some sort of configuration space) that one must take into consideration in any physical problem. Strictly speaking, they are smooth functions from M to E, where M is your manifold, and E is some sort of bundle over your manifold.


[/ QUOTE ]

ok. But is this mathematical machinery much different in principle than the old high school physics explanation that the Force Field is a collection of vectors defining the direction and magnitude of force that the field would apply at various locations? Where do these vectors come from? How do they get there? What are they made of? So now instead of just vectors we have the mathematical structures of manifolds, connections, bundles, submanifolds, smooth functions, etc. Yes these concepts model well and provide good calculations. But do they give us any better sense of answers to the above questions?

PairTheBoard

[Phil153]

[ QUOTE ]
[ QUOTE ]
There's no such thing as a force field , it's just a name we use to make the concept intuitive.

All we know is that when two objects are placed near each other, they start moving toward each other. The rest is still a mystery I believe, but I've been out of the loop a long time.

[/ QUOTE ]

Oh that's so 18th Century. You really have been out of the loop.

[/ QUOTE ]
And how exactly have we come beyond this point? Unless something has changed in the 8 or so years, I never saw any insight into the nature of the fundamental forces, merely mathematical descriptions of their effects

[thylacine]

Phil153 said:[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
There's no such thing as a force field , it's just a name we use to make the concept intuitive.

All we know is that when two objects are placed near each other, they start moving toward each other. The rest is still a mystery I believe, but I've been out of the loop a long time.

[/ QUOTE ]

Oh that's so 18th Century. You really have been out of the loop.

[/ QUOTE ]
And how exactly have we come beyond this point? Unless something has changed in the 8 or so years, I never saw any insight into the nature of the fundamental forces, merely mathematical descriptions of their effects

[/ QUOTE ]

The force fileds are physically real. They can be detected. They have mass. They are not merely convenient fictions. This was resolved in the 19th Century.

PairTheBoard said:[ QUOTE ]
[ QUOTE ]
But the general idea is that "fields" are simply attributes of the manifold (usually some sort of configuration space) that one must take into consideration in any physical problem. Strictly speaking, they are smooth functions from M to E, where M is your manifold, and E is some sort of bundle over your manifold.


[/ QUOTE ]

ok. But is this mathematical machinery much different in principle than the old high school physics explanation that the Force Field is a collection of vectors defining the direction and magnitude of force that the field would apply at various locations? Where do these vectors come from? How do they get there? What are they made of? So now instead of just vectors we have the mathematical structures of manifolds, connections, bundles, submanifolds, smooth functions, etc. Yes these concepts model well and provide good calculations. But do they give us any better sense of answers to the above questions?

PairTheBoard

[/ QUOTE ]


Now if you are saying that the fields are real, and they are modelled very well by various mathematical machinery, but that you would still like to know whats really going on in reality, then I sympathize with that point of view.

[borisp]

[ QUOTE ]
[ QUOTE ]
But the general idea is that "fields" are simply attributes of the manifold (usually some sort of configuration space) that one must take into consideration in any physical problem. Strictly speaking, they are smooth functions from M to E, where M is your manifold, and E is some sort of bundle over your manifold.


[/ QUOTE ]

ok. But is this mathematical machinery much different in principle than the old high school physics explanation that the Force Field is a collection of vectors defining the direction and magnitude of force that the field would apply at various locations? Where do these vectors come from? How do they get there? What are they made of? So now instead of just vectors we have the mathematical structures of manifolds, connections, bundles, submanifolds, smooth functions, etc. Yes these concepts model well and provide good calculations. But do they give us any better sense of answers to the above questions?

PairTheBoard

[/ QUOTE ]
For me, it seems very comforting when an "explanation" amounts to nothing more than formal mathematics. It occurs to me that in these instances, it is our demand for an intuitive explanation that needs revision, not the explanation itself.

Is it not true that you can detect these fields with your senses? Is it not true that the mathematical machinery provides an almost perfect framework to predict the content of your detections? What else is there to an explanation?

I mean, seriously, how well do you even know what matter is? Or is it simply the case that you stopped questioning its nature, since it is so trivially detected by your senses? Could it not be the case that something like force fields are simply easier for you to question?

Not trying to be a jerk here, I have asked myself these same questions. I guess I lean towards the "Copenhagen" interpretation of (quantum) physics. Von Neumann said it best: "Young man, in mathematics you don't understand things. You just get used to them." (Not implying that you are young /images/graemlins/smile.gif)

[gumpzilla]

[ QUOTE ]

Now if you are saying that the fields are real, and they are modelled very well by various mathematical machinery, but that you would still like to know whats really going on in reality, then I sympathize with that point of view.

[/ QUOTE ]

I'm pretty sure this is what your opponent was arguing about. You have to admit that "the fields are real, but I don't know what is really happening in reality" is a strange construction. From an operationalist standpoint, sure, fields are real; treating them as if they were real yields consistent results. But that's not necessarily what somebody means when somebody asks what they "really" are, and then one gets into an entire philosophy of science debate that I'm not particularly qualified for.

As for me, I tend to not think about this stuff.

[thylacine]

[ QUOTE ]
[ QUOTE ]

Now if you are saying that the fields are real, and they are modelled very well by various mathematical machinery, but that you would still like to know whats really going on in reality, then I sympathize with that point of view.

[/ QUOTE ]

I'm pretty sure this is what your opponent was arguing about. You have to admit that "the fields are real, but I don't know what is really happening in reality" is a strange construction. From an operationalist standpoint, sure, fields are real; treating them as if they were real yields consistent results. But that's not necessarily what somebody means when somebody asks what they "really" are, and then one gets into an entire philosophy of science debate that I'm not particularly qualified for.

As for me, I tend to not think about this stuff.

[/ QUOTE ]

The difference is between a mathematical abstraction of something that exists and a mathematical abstraction of something that does not exist.

[gumpzilla]

[ QUOTE ]

The difference is between a mathematical abstraction of something that exists and a mathematical abstraction of something that does not exist.

[/ QUOTE ]

What's your basis for assuming existence? It seems to me that the evidence one can point to for the existence of such things is consistency with a particular set of mathematical abstractions. So I don't really see how you distinguish between your two possibilities, as the evidence for either viewpoint appears to be the same.

[thylacine]

[ QUOTE ]
[ QUOTE ]

The difference is between a mathematical abstraction of something that exists and a mathematical abstraction of something that does not exist.

[/ QUOTE ]

What's your basis for assuming existence? It seems to me that the evidence one can point to for the existence of such things is consistency with a particular set of mathematical abstractions. So I don't really see how you distinguish between your two possibilities, as the evidence for either viewpoint appears to be the same.

[/ QUOTE ]

Okay, consider charged matter and the electromagnetic field.

Is it in any way reasonable to say that charged matter exists but that the electromagnetic field does not?

[gumpzilla]

[ QUOTE ]

Okay, consider charged matter and the electromagnetic field.

Is it in any way reasonable to say that charged matter exists but that the electromagnetic field does not?

[/ QUOTE ]

Probably not, given that the evidence for each is the same. In terms of intuitive conceptions, it is clear why matter is much easier for people to grok. We are used to dealing with localized objects and so conceiving of small pointlike particles isn't that hard, whereas there is nothing that we are familiar with materially that is a field. (Arguments about something like temperature don't convince me, because that is more of a description of the properties of some other collection of matter rather than a thing unto itself.)

This visualizability is, in my opinion, what non-philosophers generally mean when they talk about existence. We want analogs to other physical systems that we can intuit. Trying to ascribe this same kind of material existence to the field in the past led to ether theories and all of that, which were obviously flawed. I don't know of a good picture for the field that is consistent and works, other than just looking at the math of thing.

For that reason, I don't think it's terribly unfair of Phil to say "no, the field doesn't exist," and it seems unnecessarily nitpicky to me to attack that point. If there's not a meaningful way of distinguishing between existence and nonexistence in this true sense - if we can't really distinguish between "things behave this way" and "things are this way" - then what's the point? If we agree that Maxwell's equations and general relativity seem to do a good job explaining what's going on, isn't that about the limit of what we can say at the moment?

I would contrast this with issues regarding quantum mechanical interpretation. Arguments about hidden variable theories led to Bell's theorem predicting real experimental consequences for things being a certain way. This kind of discussion I am all for, obviously; whereas, in a similar vein, I find the many-worlds interpretation as it has been explained to me to be an exercise in pointlessness.

[thylacine]

[ QUOTE ]
[ QUOTE ]

Okay, consider charged matter and the electromagnetic field.

Is it in any way reasonable to say that charged matter exists but that the electromagnetic field does not?

[/ QUOTE ]

Probably not, given that the evidence for each is the same. In terms of intuitive conceptions, it is clear why matter is much easier for people to grok. We are used to dealing with localized objects and so conceiving of small pointlike particles isn't that hard, whereas there is nothing that we are familiar with materially that is a field. (Arguments about something like temperature don't convince me, because that is more of a description of the properties of some other collection of matter rather than a thing unto itself.)

This visualizability is, in my opinion, what non-philosophers generally mean when they talk about existence. We want analogs to other physical systems that we can intuit. Trying to ascribe this same kind of material existence to the field in the past led to ether theories and all of that, which were obviously flawed. I don't know of a good picture for the field that is consistent and works, other than just looking at the math of thing.

For that reason, I don't think it's terribly unfair of Phil to say "no, the field doesn't exist," and it seems unnecessarily nitpicky to me to attack that point. If there's not a meaningful way of distinguishing between existence and nonexistence in this true sense - if we can't really distinguish between "things behave this way" and "things are this way" - then what's the point? If we agree that Maxwell's equations and general relativity seem to do a good job explaining what's going on, isn't that about the limit of what we can say at the moment?

I would contrast this with issues regarding quantum mechanical interpretation. Arguments about hidden variable theories led to Bell's theorem predicting real experimental consequences for things being a certain way. This kind of discussion I am all for, obviously; whereas, in a similar vein, I find the many-worlds interpretation as it has been explained to me to be an exercise in pointlessness.

[/ QUOTE ]

Another question. Is it in any way reasonable to say that fermions exist but that bosons do not exist?

Personally, I do not <font color="red">S</font><font color="blue">E</font><font color="green">E</font> why bosons should be seen as so intangible. /images/graemlins/cool.gif

[thylacine]

[ QUOTE ]
[ QUOTE ]
[ QUOTE ]

Okay, consider charged matter and the electromagnetic field.

Is it in any way reasonable to say that charged matter exists but that the electromagnetic field does not?

[/ QUOTE ]

Probably not, given that the evidence for each is the same. In terms of intuitive conceptions, it is clear why matter is much easier for people to grok. We are used to dealing with localized objects and so conceiving of small pointlike particles isn't that hard, whereas there is nothing that we are familiar with materially that is a field. (Arguments about something like temperature don't convince me, because that is more of a description of the properties of some other collection of matter rather than a thing unto itself.)

This visualizability is, in my opinion, what non-philosophers generally mean when they talk about existence. We want analogs to other physical systems that we can intuit. Trying to ascribe this same kind of material existence to the field in the past led to ether theories and all of that, which were obviously flawed. I don't know of a good picture for the field that is consistent and works, other than just looking at the math of thing.

For that reason, I don't think it's terribly unfair of Phil to say "no, the field doesn't exist," and it seems unnecessarily nitpicky to me to attack that point. If there's not a meaningful way of distinguishing between existence and nonexistence in this true sense - if we can't really distinguish between "things behave this way" and "things are this way" - then what's the point? If we agree that Maxwell's equations and general relativity seem to do a good job explaining what's going on, isn't that about the limit of what we can say at the moment?

I would contrast this with issues regarding quantum mechanical interpretation. Arguments about hidden variable theories led to Bell's theorem predicting real experimental consequences for things being a certain way. This kind of discussion I am all for, obviously; whereas, in a similar vein, I find the many-worlds interpretation as it has been explained to me to be an exercise in pointlessness.

[/ QUOTE ]

Another question. Is it in any way reasonable to say that fermions exist but that bosons do not exist?

Personally, I do not <font color="red">S</font><font color="blue">E</font><font color="green">E</font> why bosons should be seen as so intangible. /images/graemlins/cool.gif

[/ QUOTE ]

And another couple of questions.

What does "operationalist" mean?

What does "grok" mean?

[LeadbellyDan]

Bosons definately exist.

[kerowo]

[ QUOTE ]

What does "grok" mean?

[/ QUOTE ]

It means to understand something at a 1960's group-love science-fiction pseudo-mystic-martian level.

[FortunaMaximus]

Read Heinlein and you will grok what grok is.

Short def: To completely understand and absorb the essence of something.

How has that not made it into Webster's yet? o_O

[TomTom]

Grok: When the observer and the observed merge.